\begin{figure}[H]
\begin{tikzpicture}
\tikzset{font=\small,
	level 1+/.style={level distance=40pt},
	every tree node/.style={align=center, anchor=north},
	edge from parent/.style=
	{draw,
	 edge from parent path={(\tikzparentnode.south)
							-- +(0,-8pt)
							-| (\tikzchildnode)}}
}

\Tree [
.{\{pre\} shiftRow mid \{post\}}
	[.\node[draw]{unfold shiftRow};
		[.\node[draw]{eapply hoare\_seq};
			[.{\{pre\} byte aux ::= mid[1][0] \{st$_1$\}}
				\node[draw]{apply hoare\_byte\_matrix\_asgn\_10};
			]
			[.{\{st$_1$\} mid[1][0] ::= (mid[1][1]); mid[1][1] ::= aux \{post\}}
				[.\node[draw]{eapply hoare\_seq};
					[.{\{st$_1$\} mid[1][0] ::= (mid[1][1]) \{st$_2$\}}
						\node[draw]{apply hoare\_matrix\_matr\_10\_11};
					]
					[.{\{st$_2$\} mid[1][1] ::= aux \{post\}}
						[.\node[draw]{apply hoare\_matrix\_id\_11};
						]
					]
				]
			]
		]
	]
]
\end{tikzpicture}
\caption{Árbol de prueba de hoare\_shift\_row} \label{tree:hoare_shiftrow}
\end{figure}